Light and death: photons and apoptosis

Catalytic nanotechnology of X-ray photodynamics for cancer treatments

Photodynamic therapy (PDT) has been applied in cancer treatment because of its high selectivity, low toxicity, and non-invasiveness. However, the limited penetration depth of the light still hampers from reaching deep-seated tumors. Considering the penetrating ability of high-energy radiotherapy, X-ray-induced photodynamic therapy (X-PDT) has evolved as an alternative to overcome tissue blocks. As the basic principle of X-PDT, X-rays stimulate the nanoparticles to emit scintillating or persistent luminescence and further activate the photosensitizers to generate reactive oxygen species (ROS), which would cause a series of molecular and cellular damages, immune response, and eventually break down the tumor tissue. In recent years, catalytic nanosystems with unique structures and functions have emerged that can enhance X-PDT therapeutic effects via an immune response. The anti-cancer effect of X-PDT is closely related to the following factors: energy conversion efficiency of the material, the radiation dose of X-rays, quantum yield of the material, tumor resistance, and biocompatibility. Based on the latest research in this field and the classical theories of nanoscience, this paper systematically elucidates the current development of the X-PDT and related immunotherapy, and highlights its broad prospects in medical applications, discussing the connection between fundamental science and clinical translation.

Activation of the JNKs/ATM-p53 axis is indispensable for the cytoprotection of dermal fibroblasts exposed to UVB radiation

Although UVB radiation is mainly absorbed by the epidermis, ~5-10% of its photons reach and affect the upper part of the dermis. Physiologically relevant UVB doses, able to provoke erythema, induce apoptosis in human dermal fibroblasts in vitro, as well as in the dermis of SKH-1 mice. Given the sparse and even contradictory existing information on the effect of UVB radiation on dermal fibroblasts' viability, aim of this work was to unravel the crucial signaling pathways regulating the survival of UVB-treated human dermal fibroblasts. We found that UVB radiation immediately stimulates the phosphorylation of MAPK family members, as well as Akt, and is genotoxic leading to the delayed ATM-p53 axis activation. Akt phosphorylation after UVB radiation is EGFR-mediated and EGFR inhibition leads to a further decrease of viability, while the Akt activator SC79 rescues fibroblasts to an extent by a mechanism involving Nrf2 activation. The known Nrf2 activator sulforaphane also exerts a partial protective effect, although by acting in a distinct mechanism from SC79. On the other hand, inhibition of JNKs or of the ATM-p53 axis leads to a complete loss of viability after UVB irradiation. Interestingly, JNKs activation is necessary for p53 phosphorylation, while the ATM-p53 pathway is required for the long-term activation of JNKs and Akt, reassuring the protection from UVB. Although UVB radiation results in intense and prolonged increase of intracellular ROS levels, classical anti-oxidants, such as Trolox, are unable to affect Akt, JNKs, or p53 phosphorylation and to reverse the loss of fibroblasts' viability. Collectively, here we provide evidence that the main viability-regulating UVB-triggered biochemical pathways act synergistically towards the protection of human dermal fibroblasts, with EGFR/Akt and Nrf2 serving as auxiliary anti-apoptotic machineries, while JNKs/ATM-p53 activation and interplay being overriding and indispensable for the perpetuation of cellular defense and the maintenance of cell viability.

Apoptosis and Bcl-2 Expression in Irradiated Lungs and the Effect of Pentoxifylline

We measured number of bcl-2, apoptotic, neutrophil, and surfactant apoprotein D (SP-D) positive cells in irradiated rat lungs during different time points after the sublethal whole-thorax irradiation of rats. We also investigated the influence of pentoxifylline (PTX) therapy on these markers. Wistar rats were given 15 Gy thoracic irradiation and PTX (35 mg/kg) twice a week. Animals were examined histologically and imunohistochemically at intervals from 1-12 weeks. In non-treated rats compared with treated rats, bcl-2 expression was significantly inhibited from 4 weeks after irradiation. A higher apoptosis presence in non-treated rats from 4 weeks was found and apoptosis development in PTX-treated animals was delayed and started 8 weeks after irradiation. Similar differences were measured during neutrophil granulocytes examination. Neutrophil penetration in non-treated rats was found 5 weeks after irradiation in contrast to the RP onset of PTX-treated animals 8 weeks after irradiation. The number of SP-D positive cells in non-treated rats observed until 5 weeks after irradiation was higher than in the control group. PTX-treated animals expressed higher number of SP-D positive cells during the whole experiment than the control group. We suggest that apoptosis is linked to neutrophil granulocyte actions during the RP onset and that PTX-therapy causes diminished inflammation development.

Exponentially increasing incidences of cutaneous malignant melanoma in Europe correlate with low personal annual UV doses and suggests 2 major risk factors

For several decades the incidence of cutaneous malignant melanoma (CMM) steadily increased in fair-skinned, indoor-working people around the world. Scientists think poor tanning ability resulting in sunburns initiate CMM, but they do not understand why the incidence continues to increase despite the increased use of sunscreens and formulations offering more protection. This paradox, along with lower incidences of CMM in outdoor workers, although they have significantly higher annual UV doses than indoor workers have, perplexes scientists. We found a temporal exponential increase in the CMM incidence indicating second-order reaction kinetics revealing the existence of 2 major risk factors. From epidemiology studies, we know one major risk factor for getting CMM is poor tanning ability and we now propose the other major risk factor may be the Human Papilloma Virus (HPV) because clinicians find β HPVs in over half the biopsies. Moreover, we uncovered yet another paradox; the increasing CMM incidences significantly correlate with decreasing personal annual UV dose, a proxy for low vitamin D3 levels. We also discovered the incidence of CMM significantly increased with decreasing personal annual UV dose from 1960, when it was almost insignificant, to 2000. UV and other DNA-damaging agents can activate viruses, and UV-induced cytokines can hide HPV from immune surveillance, which may explain why CMM also occurs in anatomical locations where the sun does not shine. Thus, we propose the 2 major risk factors for getting CMM are intermittent UV exposures that result in low cutaneous levels of vitamin D3 and possibly viral infection.

The circadian control of skin and cutaneous photodamage

Biologically, light including ultraviolet (UV) radiation is vital for life. However, UV exposure does not come without risk, as it is a major factor in the development of skin cancer. Natural protections against UV damage may have been affected by lifestyle changes over the past century, including changes in our sun exposure due to working environments, and the use of sunscreens. In addition, extended "day time" through the use of artificial light may contribute to the disruption of our circadian rhythms; the daily cycles of changes in critical bio-factors including gene expression. Circadian disruption has been implicated in many health conditions, including cardiovascular, metabolic and psychiatric diseases, as well as many cancers. Interestingly, the pineal hormone melatonin plays a role in both circadian regulation as well as protection from UV skin damage, and is therefore an important factor to consider when studying the impact of UV light. This review discusses the beneficial and deleterious effects of solar exposure, including UV skin damage, Vitamin D production, circadian rhythm disruption and the impact of melatonin. Understanding these benefits and risks is critical for the development of protective strategies against solar radiation.

Heat-shock-induced cellular responses to temperature elevations occurring during orthopaedic cutting

Severe heat-shock to bone cells caused during orthopaedic procedures can result in thermal damage, leading to cell death and initiating bone resorption. By contrast, mild heat-shock has been proposed to induce bone regeneration. In this study, bone cells are exposed to heat-shock for short durations occurring during surgical cutting. Cellular viability, necrosis and apoptosis are investigated immediately after heat-shock and following recovery of 12, 24 h and 4 days, in osteocyte-like MLO-Y4 and osteoblast-like MC3T3-E1 cells, using flow cytometry. The regeneration capacity of heat-shocked Balb/c mesenchymal stem cells (MSCs) and MC3T3-E1s has been investigated following 7 and 14 day's recovery, by quantifying proliferation, differentiation and mineralization. An immediate necrotic response to heat-shock was shown in cells exposed to elevated temperatures (45°C, 47°C and most severe at 60°C). A longer-term apoptotic response is induced in MLO-Y4s and, to a lesser extent, in MC3T3-E1s. Heat-shock-induced differentiation and mineralization by MSCs. These findings indicate that heat-shock is more likely to induce apoptosis in osteocytes than osteoblasts, which might reflect their role as sensors detecting and communicating damage within bone. Furthermore, it is shown for the first time that mild heat-shock (less than equal to 47°C) for durations occurring during surgical cutting can positively enhance osseointegration by osteoprogenitors.

Metal-catalyzed proteolysis, conformational antigenicity, photosensitized oxidation, and electrical dysfunction explain the pathogenicity of protein aggregates

It is widely accepted that protein aggregates tend to be pathologic, although little is known about why they are pathologic. Here, we summarize published findings about protein aggregates which have implications for pathology, but which have not yet been covered in any review or hypothesis on the subject, to the best of our knowledge. These findings suggest that protein aggregates can: (i) act as proteases, using exposed surface serines, (ii) function as immunogens, using novel conformational epitopes, (iii) behave as photosensitization-aids, using a novel peptide-based fluorescence, and (iv) act as electrical conductors, using electrons tunneling through hydrogen-bonded networks of peptide bonds. The potential pathological consequences of each finding are speculated upon.

The protective effects of ultraviolet A1 irradiation on spontaneous lupus erythematosus-like skin lesions in MRL/lpr mice

We investigated the effects of ultraviolet A1 (UVA1) irradiation on spontaneous lupus erythematosus- (LE-) like skin lesions of MRL/lpr mice, using a disease prevention model. UVA1 irradiation significantly inhibited the development of LE-like skin lesions, without obvious changes of the disease including renal disease and serum antinuclear antibody levels. Besides the massive infiltration of mast cells in the LE-like skin lesions, in the nonlesional skins, more mast cells infiltrated in the UVA1-irradiated group compared with the nonirradiated group. Although apoptotic cells were remarkably seen in the dermis of UVA1-irradiated mice, those cells were hardly detectable in the dermis of the nonirradiated mice without skin lesions. Further analysis showed that some of those apoptotic cells were mast cells. Thus, UVA1 might exert its effects, at least in part, through the induction of the apoptosis of pathogenic mast cells. Our results supported the clinical efficacy of UVA1 irradiation for skin lesions of lupus patients.

Photodynamic therapy for palpebral and conjunctival proliferative vascular tumors: clinical case report

Photodynamic therapy (PDT) has been widely used in ophthalmology for the treatment of diverse pathologies, but no experience has been reported in the handling of patients with palpebral vascular and conjunctive malformations with PDT, we describe the case of one patient with a palpebral proliferative vascular tumor, treated successfully using the PDT as a new treatment alternative.

High-dose ultraviolet light exposure reduces scar hypertrophy in a rabbit ear model

BACKGROUND

The effects of ultraviolet light exposure on scar pigmentation are well documented. There is a commonly held belief among physicians that sun exposure may also worsen the appearance of fresh scars and result in excess collagen deposition. However, few studies have documented a relationship between ultraviolet light exposure and hypertrophic scarring. This study sought to evaluate the effect of ultraviolet light exposure on scar hypertrophy in an established rabbit model of cutaneous scarring.

METHODS

Four 7-mm ulcers were created on the ventral ears of eight rabbits. Starting on postoperative day 15, half of the wounds were exposed to ultraviolet-B radiation daily for either 7 or 14 days. Ultraviolet-B-exposed (n = 16) and control (n = 16) scars were harvested on postoperative day 32 for histologic and reverse-transcriptase polymerase chain reaction analysis.

RESULTS

Exposure to ultraviolet-B radiation for 7 or 14 days was associated with a 52 percent (p < 0.01) or 74 percent (p < 0.05) reduction in scar volume, respectively, compared with controls. In wounds subjected to ultraviolet-B radiation for 14 days, collagen type I-alpha2 mRNA expression was 29 percent lower than in controls (p < 0.05). There was no difference in the mRNA expression of transforming growth factor-beta1.

CONCLUSION

: These short-term observations demonstrate that ultraviolet-B radiation exposure reduces scar hypertrophy in this clinically relevant animal model. A reduction in collagen production or increase in collagen breakdown may account for this result. However, sunscreen should still be used as primary protection when skin is exposed to direct sunlight.

Radiation Sources Providing Increased UVA/UVB Ratios Attenuate the Apoptotic Effects of the UVB Waveband UVA-Dose-Dependently in Hairless Mouse Skin

UV radiation-induced epidermal apoptotic sunburn cells provide a mechanism for eliminating cells with irreparable DNA damage. The UVB (290-320 nm) waveband is mainly responsible, but the role of UVA (320-400 nm) is less clear, and possible waveband interactions have not been examined. Recent studies in mice reveal a protective role for UVA against UVB-induced inflammation and immunosuppression, mediated via cutaneous heme oxygenase (HO). As HO has antiapoptotic properties in other tissues, this study examines the effect of UVA/UVB waveband interaction on apoptosis in the Skh:hr-1 hairless mouse epidermis. Apoptosis was assessed by sunburn cell number, caspase-3-positive cell number, and degree of DNA fragmentation, in mice exposed to radiation sources providing a constant UVB dose with increasing proportions of UVA. The results indicated that as the UVA/UVB ratio was increased, both the sunburn cell and caspase-3-positive cell number decreased, and the degree of DNA fragmentation was reduced. Treatment of mice with the HO inhibitor, tin protoporphyrin-IX, markedly reduced the UVA antiapoptotic effect, confirming a major role for HO. The observations suggest that UVA reduces UVB-induced DNA damage, and may therefore have anti-photocarcinogenic properties that could be harnessed for better photoprotection in humans.

Effects of topical glutathione treatment in rat ischemic wound model

Oxidative stress secondary to ischemia can cause physiopathologic changes that adversely affect wound healing. In this experimental study, we hypothesized that the topical use of esterified glutathione, a well-known antioxidant, can minimize the effects of oxidative stress by an increase in intracellular glutathione and accelerate wound healing by increasing the contraction capacity of fibroblasts and preventing keratinocytes from apoptosis in a rat ischemic wound model. Experimental models were divided into 3 groups as treatment, control, and healthy. Bipedicled flaps were elevated from the dorsum of the rats, and 6-mm punch wounds were created at the end of the first day when the ischemia is most apparent. Wounds were followed histopathologically and immunohistochemically, and matrix metalloproteinase (MMP)-1 and tissue inhibitors of metalloproteinase (TIMP-1) levels were measured by ELISA. Samples were collected at 0, 5, 8, 10, and 12 days. Histopathologic evaluation revealed significant extracellular matrix deposition and reepithelization every fifth day in treatment and healthy groups when compared with control group. Immunohistochemical evaluation revealed increased apoptosis in basal keratinocytes in the control group when compared with the other groups. The evaluation of the samples collected at 5 and 8 days revealed increased MMP-1 levels in treatment and control groups, but the increase in TIMP-1 levels was more significant than MMP-1 levels in treatment group. MMP-1/TIMP-1 ratio was significantly low in the treatment group.Our results showed that topical GSH treatment can reduce oxidative stress, and the reestablishment of the MMP-1/TIMP-1 ratio gives way to adequate and regular extracellular matrix production and reepithelization. It is concluded that esterified GSH, which is experimentally shown to be effective in ischemic wound healing, can be used clinically in ischemic wounds.

Mechanisms of cell death in oxidative stress

Reactive oxygen or nitrogen species (ROS/RNS) generated endogenously or in response to environmental stress have long been implicated in tissue injury in the context of a variety of disease states. ROS/RNS can cause cell death by nonphysiological (necrotic) or regulated pathways (apoptotic). The mechanisms by which ROS/RNS cause or regulate apoptosis typically include receptor activation, caspase activation, Bcl-2 family proteins, and mitochondrial dysfunction. Various protein kinase activities, including mitogen-activated protein kinases, protein kinases-B/C, inhibitor-of-I-kappaB kinases, and their corresponding phosphatases modulate the apoptotic program depending on cellular context. Recently, lipid-derived mediators have emerged as potential intermediates in the apoptosis pathway triggered by oxidants. Cell death mechanisms have been studied across a broad spectrum of models of oxidative stress, including H2O2, nitric oxide and derivatives, endotoxin-induced inflammation, photodynamic therapy, ultraviolet-A and ionizing radiations, and cigarette smoke. Additionally ROS generated in the lung and other organs as the result of high oxygen therapy or ischemia/reperfusion can stimulate cell death pathways associated with tissue damage. Cells have evolved numerous survival pathways to counter proapoptotic stimuli, which include activation of stress-related protein responses. Among these, the heme oxygenase-1/carbon monoxide system has emerged as a major intracellular antiapoptotic mechanism.

Keratinocyte apoptosis in epidermal development and disease

Keratinocyte (KC) apoptosis plays a critical role in regulating epidermal development and restraining carcinogenesis. Apoptosis balances proliferation to maintain epidermal thickness, contributes to stratum corneum formation and may eliminate pre-malignant cells. Apart from the normal developmental program, KC apoptosis can be triggered by UV light and other stimuli. Dysfunctional apoptosis occurs in some skin diseases, such as psoriasis and skin cancer. Here we review the current state of knowledge of KC apoptosis, with particular focus on apoptotic signaling pathways and molecular mechanisms of apoptosis control, and discuss new insights into the complex role of apoptosis in skin carcinogenesis that are emerging from mouse models.

Influence of substitutions on asymmetric dihydroxychlorins with regard to intracellular uptake, subcellular localization and photosensitization of Jurkat cells

The search for new efficient sensitizers for photodynamic therapy (PDT) points to improve photophysical properties like absorption in the red region and singlet oxygen quantum yield as well as to control the localization of the sensitizer within the tumour cell. Depending on their physicochemical properties and their uptake mechanism, sensitizers can reach different intracellular concentrations and localize in different subcellular compartments. Moreover, the preferential localization of a sensitizer in target organelles, like mitochondria or lysosomes, could determine the cell death mechanism after PDT. This study aimed to investigate the influence of substitutions on dihydroxychlorins with regard to intracellular uptake, subcellular localization and cell death pathway. Moreover, the effect of a liposome-based delivery system was tested. The intracellular uptake was found to be strictly dependent on the sensitizer molecular structure and the means of its delivery. The most polar sensitizer in this study (compound 3) had, depending on incubation time, an intracellular concentration 2-8 times higher than the unsubstituted chlorin 1. All investigated photosensitizers localize predominantly in lysosomes but after longer incubation times weak fluorescence intensity was also detected in mitochondria and Golgi apparatus. The cell death pathway was found to be influenced by the sensitizer intracellular concentration and the applied light doses. In general, the increasing amphiphilicity of the sensitizer molecules is correlated with an increased sensitizer uptake and an increased rate of necrotic cells after irradiation.

Phototherapy and photochemotherapy of sclerosing skin diseases

The treatment of sclerosing skin diseases [systemic sclerosis, localized scleroderma, lichen sclerosus et atrophicus, sclerodermoid graft-vs.-host disease, scleredema adultorum (Buschke), scleromyxedema and necrobiosis lipoidica] is difficult and remains a great challenge. Numerous treatments, some with potentially hazardous side effects, are currently used with only limited success. The introduction of phototherapy and photochemotherapy for sclerosing skin diseases has considerably enriched the therapeutic panel and proven useful in a number of sclerosing skin diseases especially in localized scleroderma. Two phototherapeutic modalitites are used for the treatment of sclerosing skin diseases, long-wave ultraviolet A and psoralen plus ultraviolet A (PUVA). This article reviews current knowledge about the application of phototherapy and photochemotherapy to various sclerosing skin disorders.

Ultraviolet-A1 (340-400 nm)-mediated receptor and cytokine changes of transformed lymphocytes

BACKGROUND

Ultraviolet-A1 (340-400 nm) (UVA1) radiation causes singlet-oxygen damage that depolarizes mitochondrial membranes triggering immediate apoptosis (T < or = 4 h), while it also causes oxidative damage to DNA inducing delayed apoptosis (T > or = 24 h). In this study, we examined some potential therapeutic endpoints associated with UVA1-mediated immediate and delayed apoptosis, such as receptor and cytokine changes.

METHODS

We quantified the number of membrane-bound CD3 receptors on transformed T lymphocytes (Jurkat) and the number of membrane-bound CD19 receptors on transformed B lymphocytes (Daudi) using flow cytometry. We also quantified the release of the cytokines interferon gamma (IFN-gamma) and interleukin-2 (IL-2) using enzyme-linked immunosorbent assays.

RESULTS

Out of the entire population of cells, only the apoptotic Daudi cells immediately decreased CD19 expression via capping, while only the apoptotic Jurkat cells increased CD3 receptor expression 24 h post-exposure. Both receptor changes occurred in a UVA1 dose-dependent manner. We also examined other T-cell receptors, such as CD4, CD25, and CD69, but they did not change for up to 24 h following exposure. During UVA1-triggered immediate apoptosis of Jurkat T cells, IFN-gamma levels increased in a dose-dependent manner at 4 h, but returned to baseline levels at 24 h post-exposure, whereas, there was no significant change in IL-2 at 4 or 24 h.

CONCLUSION

Thus, UVA1-triggered immediate apoptosis causes a rapid decrease in the number of CD19 receptors on Daudi B cells and release of IFN-gamma from Jurkat T cells at 4 h, and UVA1-mediated delayed apoptosis causes an increase in the number of CD3 receptors on Jurkat T cells.

Ultraviolet A Irradiation Induces NF-E2-Related Factor 2 Activation in Dermal Fibroblasts: Protective Role in UVA-Induced Apoptosis

Ultraviolet (UV) radiation is one of the most important environmental factors involved in the pathogenesis of skin aging and cancer. Many harmful effects of UV radiation are associated with the generation of reactive oxygen species, and cellular antioxidants act to prevent the occurrence and reduce the severity of UV-induced skin disorders. Transcription factor NF-E2-related Factor 2 (Nrf2) and its cytoplasmic anchor protein Kelch-like-ECH-associated protein 1 (Keap1) are central regulators of the cellular antioxidant response. In this study, we investigated the effects of UV irradiation on the activation of Nrf2 in dermal fibroblasts. We found that UVA irradiation, but not UVB, causes nuclear translocation and accumulation of Nrf2 by a factor of 6.5 as compared with unirradiated controls. The nuclear accumulation of Nrf2 induced by UVA was enhanced by the photosensitizer hematoporphyrin. To evaluate the protective role of Nrf2 against UVA radiation, we examined UVA-induced apoptosis using dermal fibroblasts derived from nrf2 or keap1 gene knockout mice. Whereas disruption of nrf2 increased the number of apoptotic cells following UVA irradiation by 1.7-fold, disruption of keap1 decreased the apoptotic cell number by half as compared with wild-type controls. These findings thus demonstrate that the Nrf2-Keap1 pathway plays an important role in the protection of the skin against UVA irradiation.

Systematic Evaluation of Anti-apoptotic Growth Factor Signaling in Vascular Smooth Muscle Cells

Peptide growth factors contribute to the pathogenesis of cardiovascular diseases by inducing a variety of cellular responses including anti-apoptotic effects. Several of the signaling molecules that are activated by growth factor receptors such as Src family kinases (Src), phosphatidylinositol 3'-kinase (PI3K), phospholipase Cgamma (PLCgamma), Ras, and SHP-2 were shown to mediate survival signals. We systematically investigated the relative contribution of each signaling molecule for growth factor-dependent cell survival in vascular smooth muscle cells (VSMC). Our approach was the use of mutated plateletderived growth factor (PDGF) beta-receptors (betaPDGFR) in which the tyrosine residues required for binding of each signaling molecule were individually mutated to phenylalanine. To bypass endogenous PDGFR in VSMC we used chimeric receptors (ChiRs), containing the extracellular domain of the macrophage colony-stimulating factor (M-CSF) receptor and the cytoplasmic domain of the wild type (WT) or mutated betaPDGFR. Selective activation of the ChiR-WT with M-CSF significantly reduced apoptosis to the same extent as PDGF-BB in non-transfected cells. Deletion of the binding site for PI3K, but not for Src, RasGAP, SHP-2, or PLCgamma, completely abolished the anti-apoptotic effect. Consistently, a ChiR mutant that only binds PI3K was fully able to mediate cell survival as efficiently as the ChiR-WT. Furthermore, the PDGF-dependent anti-apoptotic effect in non-transfected cells was completely abolished by the PI3K inhibitor wortmannin, whereas inhibitors of Src, PLCgamma, ERK, or p38 MAP kinase had no effect. The exploration of downstream signaling events revealed that PDGF-BB activates the anti-apoptotic Akt signaling pathway in a PI3K-dependent manner. Moreover, Akt phosphorylates and thus inactivates the pro-apoptotic proteins BAD and Forkhead transcription factors (FKHR, FKHRL1). We conclude that growth factor-dependent cell survival in VSMC is mediated only by activation of the PI3K/Akt pathway, whereas all other receptor-associated signaling molecules do not play a significant role.

UV Doses Worldwide†

UV radiation affects human health. Human exposure to UV radiation causes a few beneficial health effects like vitamin D3 formation but it causes many detrimental health effects: sunburn, ocular damage, photoaging, immune suppression, DNA damage and skin cancer. In countries with fair-skinned populations, skin cancer is the most diagnosed of all cancers. In the United States in 2002, there were over one million new skin cancer cases. That means one out of every 285 people got skin cancer. Skin cancer of fair-skinned individuals is increasing at an alarming rate (4-6% per year) around the world and has now reached so-called "pandemic" proportions. Thus, it is important to know what UV doses people around the world get throughout their lives. This review covers how the outdoor UV doses are weighted for different biological effects, the most commonly used measuring devices for terrestrial and personal UV doses, the natural and other effects on terrestrial and personal UV doses, the time people spend outside, their ambient exposures and the terrestrial and personal UV doses of adult outdoor and indoor workers as well as children and adolescents around the world. Overall, outdoor-working adults get about 10%, while indoor-working adults and children get about 3% (2-4%) of the total available annual UV (on a horizontal plane). People's UV doses increase with increasing altitude and decreasing latitude; most indoor-working adult Europeans get 10,000-20,000 J/m2 per year, Americans get 20,000-30,000 J/m2 per year and Australians are estimated to get 20,000-50,000 J/m2 per year (excluding vacation, which can increase the dose by 30% or more).

Innovative therapies: photodynamic therapy

Photodynamic diagnosis could be a useful tool for improving the diagnostic yield of tumor biopsy, especially for mesothelioma tumors that are sclerotic and particularly hypocellular. For PDD, the use of low doses of a sensitizing drug, such as 5-ALA, must be investigated further. The initial results of 5-ALA-mediated PDD are promising. The role, if any, for PDT in the treatment of mesothelioma has yet to be established. The number of centers exploring this technology is limited because the procedure is labor intensive and requires not only specialized equipment but also physician support. The number of patients treated in the different trials is small, and no definitive conclusions can be drawn. Further complicating the interpretation of published results is the number of variables (i.e., type of sensitizer, light dose, drug dose, drug light interval, methods of light measurement, technique of light delivery, surgical debulking techniques), which differ between studies. Most reports are phase I and II studies. The final outcome of these studies with respect to survival is of limited value. The only phase III study, which was performed with an earlier generation photosensitizer, reported no advantage to the use of PDT in combination with surgery and immunochemotherapy. To date, the most that can be said is that intraoperative PDT can be performed safely in experienced centers and that there are some encouraging results, especially in patients with stages I and II MPM, particularly with the newer generation photosensitizers. One attractive aspect of this adjuvant treatment is that PDT, as opposed to some of the other adjuvant treatments combined with surgery, may offer the option of effecting adequate tumor debulking with a pulmonary-sparing procedure.

Oral Polypodium leucotomos extract decreases ultraviolet-induced damage of human skin

BACKGROUND

UV radiation induces damage to human skin. Protection of skin by an oral photoprotective agent would have substantial benefits. Objective We investigated the photoprotective effect of oral administration of an extract of the natural antioxidant Polypodium leucotomos (PL).

METHODS

A total of 9 healthy participants of skin types II to III were exposed to varying doses of artificial UV radiation without and after oral administration of PL (7.5 mg/kg). At 24 hours after exposure the erythema reaction was assessed and paired biopsy specimens were obtained from PL-treated and untreated skin.

RESULTS

A significant decrease in erythema was found in PL-treated skin (P < .01). Histologically, PL-treated biopsy specimens showed less sunburn cells (P < .05), cyclobutane pyrimidine dimers (P < .001), proliferating epidermal cells (P < .001), and dermal mast cell infiltration (P < .05). A trend toward Langerhans cell preservation was seen.

CONCLUSION

Oral administration of PL is an effective systemic chemophotoprotective agent leading to significant protection of skin against UV radiation.

Different susceptibility of malignant versus nonmalignant human T cells toward ultraviolet A-1 radiation-induced apoptosis

Ultraviolet (UV) A-1 (340-400 nm) radiation is highly effective in inducing apoptosis in skin-infiltrating T cells and thereby exerts beneficial effects in patients with T cell-mediated skin diseases. In this in vitro study, we report that malignant and normal T cells differ in their susceptibility toward UVA-1 radiation-induced apoptosis. Dose-response studies revealed that malignant CD4+ T cells isolated from a patient with adult T cell leukemia and Sezary's syndrome as well as malignant T cell lines exhibited a significantly higher susceptibility toward UVA-1 radiation-induced apoptosis 4 h (early apoptosis) and 24 h (late apoptosis) after exposure than normal, CD4+ T cells. This difference was specific for UVA-1 irradiation because it was not detected when apoptosis was induced in these cells through exposure to UVB radiation or stimulation with cell-permeable ceramides. It has been shown that UVA-1 radiation-induced T cell apoptosis is initiated through the generation of singlet oxygen. This is in agreement with the present observation that stimulation of unirradiated cells with a singlet oxygen-generating system induced apoptosis in malignant cells to a greater extent than in normal cells. Moreover, downregulation of FAS surface expression in malignant T cells was associated with the inhibition of UVA-1 radiation/singlet oxygen-induced apoptosis in these cells. It was thus of great interest to learn that addition of the caspase inhibitor Z-VADfmk decreased and interferon-gamma stimulation, which is known to upregulate caspase levels including caspase-3, increased the sensitivity of T cells toward UVA-1 radiation-induced apoptosis. Furthermore, malignant T cells had significantly higher procaspase-3 levels when compared with normal cells. These studies indicate that the susceptibility of human T cells toward UVA-1 radiation-induced apoptosis is related to the availability of caspases such as caspase-3 and that strategies directed at upregulating caspase levels will increase the efficacy of UVA-1 phototherapy.

Cellular uptake and metabolism of flavonoids and their metabolites: implications for their bioactivity

Flavonoids have been proposed to act as beneficial agents in a multitude of disease states, including cancer, cardiovascular disease, and neurodegenerative disorders. The biological effect of these polyphenols and their in vivo circulating metabolites will ultimately depend on the extent to which they associate with cells, either by interactions at the membrane or more importantly their uptake. This review summarises the current knowledge on the cellular uptake of flavonoids and their metabolites with particular relevance to further intracellular metabolism and the generation of potential new bioactive forms. Uptake and metabolism of the circulating forms of flavanols, flavonols, and flavanones into cells of the skin, the brain, and cancer cells is reviewed and potential biological relevance to intracellular formed metabolites is discussed.

Orally administered polypodium leucotomos extract decreases psoralen-UVA–induced phototoxicity, pigmentation, and damage of human skin

BACKGROUND

The use of psoralen-UVA (PUVA) in patients of skin phototype I to II is limited by side effects of acute phototoxicity and possible long-term carcinogenesis.

OBJECTIVE

We sought to assess oral Polypodium leucotomos (PL) extract in decreasing PUVA-induced phototoxicity of human skin on a clinical and histologic level.

METHODS

A total of 10 healthy patients with skin phototypes II to III were exposed to PUVA alone (using 0.6 mg/kg oral 8-methoxypsoralen) and to PUVA with 7.5 mg/kg of oral PL.

RESULTS

Clinically, phototoxicity was always lower in PL-treated skin after 48 to 72 hours (P<.005), and pigmentation was also reduced 4 months later. Histologically, PL-treated skin showed a significant numeric reduction of sunburn cells (P=.05), preservation of Langerhans cells (P< or =.01), decrease of tryptase-positive mast cell infiltration (P<.05), and decrease of vasodilation (P< or =.01). No differences were found in Ki-67+ proliferating cells.

CONCLUSIONS

PL is an effective chemophotoprotector against PUVA-induced skin phototoxicity and leads to substantial benefits of skin protection against damaging effects of PUVA as evidenced by histology.

Ultraviolet irradiation induces apoptosis in human immature, but not in skin mast cells

As diverse pruritic cutaneous diseases respond to ultraviolet treatment, we have examined whether ultraviolet light is capable of inducing apoptosis in mast cells. Human mast cell line 1 (HMC1) derived from a patient with malignant mastocytosis and purified skin mast cells were irradiated with single doses of ultraviolet B or ultraviolet A1, or pretreated with 8-methoxypsoralen prior to ultraviolet A1 exposure. After 0 to 48 h of incubation, the percentage of apoptotic and dead cells was assessed. In HMC1 cells, morphologic features of apoptosis were further evaluated by electron microscopy. All ultraviolet treatment induced apoptosis of HMC1 cells in a time- and dose-dependent manner. Apoptosis was associated with activation of caspase-3, release of cytochrome C, cleavage of poly(ADP-ribose)-polymerase, and nuclear accumulation of p53. In contrast, resting skin mast cells were resistant to ultraviolet light induced apoptosis. After incubation with stem cell factor and interleukin-4 for 2 wk, however, slowly proliferating skin mast cells also underwent apoptosis in response to ultraviolet light. In conclusion, these data demonstrate that ultraviolet light directly affects mast cells, but mainly aims at the proliferating mast cells as found in mastocytosis and mast cell dependent pruritic diseases, where increased numbers are observed due to the recruitment mast cell precursors from the blood.

Involvement of oxidative stress in apoptosis induced by a mixture of isothiazolinones in normal human keratinocytes

A 3:1 combination of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI) is widely used to preserve cosmetic products. We show here that CMI/MI induced apoptosis in normal human keratinocytes (NHK) as at low concentrations (0.001-0.05% documented by subdiploid DNA content and phosphatidylserine exposure, while at the highest concentration (0.1% as supplied, 15 p.p.m.) the response was necrosis. Various molecular events accompanied the cytotoxic effects of CMI/MI. Generation of ROS and hyperpolarization of mitochondrial transmembrane potential (DeltaPsim) were early events, followed by increased Fas expression and activation of caspase-8, and then activation of caspase-3 and -9. The drop in DeltaPsim occurred only later in the cell death pathway, when NHK showed signs of apoptosis. Pretreatment of cells for 2 h with the redox-active agent N-acetyl-L-cysteine conferred complete protection against the CMI/MI-induced cytotoxic effects, DeltaPsim loss, and apoptosis. The pan-caspase inhibitor Z-Val-Ala-Asp(OMe)-CH2F blocked the CMI/MI-induced apoptosis without preventing ROS generation and the drop in DeltaPsim. These results indicate that the generation of ROS plays an important part in mediating apoptosis and necrosis associated with CMI/MI treatment. This new aspect of the in vitro toxicity of CMI/MI may provide important information about the relationship between the preservative's in vitro apoptotic activity and its in vivo toxicity.

Antioxidants in dermocosmetology: from the laboratory to clinical application

Oxygen situated in cutaneous cells can be activated by light. This makes the integumentary apparatus particularly vulnerable to oxidative damage and is responsible for the immediate cutaneous damage that is the basis of late phenomena, such as photo-induced ageing and tumours. Thus, the cosmetic industry has undertaken research and development into antioxidant-based products able to protect the skin from the effect of pro-oxidizing noxae. This review re-examines both antioxidants suitable for dermatological application and skin care products with antioxidant capacity, as well as the laboratory methods used to evaluate the effects and in vivo efficacy of antioxidants.

Selenium protects primary human keratinocytes from apoptosis induced by exposure to ultraviolet radiation

The generation of reactive oxygen species has been implicated in ultraviolet radiation (UVR)-induced skin damage. In mice, increasing dietary selenium intake protects skin from UVR-induced DNA damage and photocarcinogenesis. We sought to determine whether selenium supplementation could protect keratinocytes from apoptosis resulting from exposure to broadband (TL20W/12) UVR. Unirradiated cultures contained 6.5 +/- 1% apoptotic cells; the maximum percentage of apoptotic cells (34 +/- 5%) was seen 16 h after UVR of 600 J/m(2). Under these conditions cell death from necrosis was 15 +/- 2.5% of the total cells. A 24-h preincubation with sodium selenite (10 nm(-1) microm) or selenomethionine (50 nm(-1) microm) protected cultured human keratinocytes from UVR-induced apoptosis. In primary keratinocytes the greatest reduction in apoptosis was found with 100 nm of either selenium compound (71% reduction in the numbers of total apoptotic cells; P < 0.01). Supplementation with 100-200 nm selenite or selenomethionine prevented UVR-induced apoptosis, but did not decrease the levels of UVR-induced p53, as measured by Western blotting. Collectively, this data suggests that selenium prevents UVR-induced cell death by inhibiting p53-independent cell death pathways.

Histological changes and involvement of apoptosis after photodynamic therapy for actinic keratoses

BACKGROUND

Photodynamic therapy (PDT), which employs a combination of a tumour-localizing photosensitizer and visible light, has been used to treat superficial malignancies in the epidermis.

OBJECTIVES

To examine histological changes and the role of apoptosis in lesions of actinic keratosis (AK) after PDT using 5-aminolaevulinic acid (ALA) and excimer dye laser.

METHODS

After topical ALA-PDT, biopsy specimens were collected from 18 skin lesions in 15 patients with AK. Paraffin-embedded sections of the skin specimens were stained with haematoxylin and eosin. The detection of apoptosis was performed using a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) method, antiactivated caspase-3 antibody and anti-Fas antibody.

RESULTS

One hour after PDT, cells with eosinophilic cytoplasm and markedly stained nuclei were found, and vacuolation of some tumour cells was noted in the lower layer of the epidermis. An infiltrate of lymphocytes and neutrophils was observed in the upper layer of the dermis. One day after PDT, all layers of the epidermis exhibited slightly degenerative necrosis, with shadow cell formation and chromatin condensation around the nuclear membrane in the lower layer of the epidermis. Necrosis in all layers of the epidermis and lymphocyte infiltration in the dermis were found 3 days after PDT. Tumour cells had disappeared and regenerative thickening of the epidermis was observed 7 days after PDT. TUNEL staining revealed apoptosis-positive cells in the epidermis in 8 of 11 specimens obtained 1 day after PDT. Activated caspase-3 expression was noted in the lower layer of the epidermis in four of these eight TUNEL-positive specimens.

CONCLUSIONS

Results suggested that apoptosis is involved in tumour cell death after PDT in patients with AK, and that it occurs within 1 day after PDT.

The sunburn cell revisited: an update on mechanistic aspects

The sunburn cell (SBC), with its pyknotic nucleus and eosinophilic cytoplasm, is characteristic of mammalian epidermis after exposure to UVC and UVB radiation or UVA radiation in the presence of psoralens. SBC may be regarded as an example of apoptosis: controlled individual cell death. Since the discovery of apoptosis over thirty years ago, there has been a considerable increase in the knowledge of mechanisms involved in this process. DNA damage has been shown to be a major determinant of SBC production both in a p53-dependent and -independent manner. Extranuclear events such as activation of membrane bound death receptors also contribute to SBC formation. The development of new technologies and techniques has resulted in a better understanding of the mechanisms and machinery involved in apoptosis, triggered by various stimuli and in different cell types. Of particular importance has been the elucidation of regulatory molecules such as caspases, inhibitor of apoptosis proteins (IAP) and the role of mitochondria as key to the process of apoptosis and consequent production of SBC. This review attempts to give an update on those mechanisms involved and the occurrence and relevance of SBC in mammalian skin are discussed.

Acoustic cavitation in phacoemulsification: chemical effects, modes of action and cavitation index

High-intensity ultrasound (US) energy (HIUE) has been extensively used in the last 3 decades in a wide range of surgical procedures, including phacoemulsification. The generation of radicals and sonoluminescence (SL) by application of continuous-wave (CW) HIUE to an aqueous medium under conditions simulating cataract phacoemulsification surgery is demonstrated by electron paramagnetic resonance (EPR) spectroscopy and a sensitive photon-detecting system. The findings provide direct evidence for the generation of acoustic cavitation in the simulated intraocular environment, pointing out that generation of acoustic cavitation in clinical phacoemulsification and other surgical applications of US is possible. The findings imply that the effects of acoustic cavitation in aqueous medium may contribute to the endothelial damage observed clinically following phacoemulsification cataract surgery. Saturation of the irrigating solution with various gases modifies the acoustic cavitation. Saturation of the irrigating solution with CO2 practically eliminates acoustic cavitation, with the concomitant elimination of radicals and SonL. CO2 may be utilized clinically to suppress acoustic cavitation in phacoemulsification and other medical applications. A cavitation index (CI) is introduced for the purpose of standardizing phacoemulsification instrumentation and other medical US devices that employ HIUE.

In vitro ultraviolet irradiation induces pro-inflammatory responses in cells from premorbid SLE mice

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease, in which sunlight (especially its ultraviolet radiation (UVR)) is known to induce exacerbation of cutaneous lesions as well as systemic manifestations of the disease. The aim of this in vitro study was to investigate whether UVR (UVA, UVB) amplifies pro-inflammatory factors in cultured dermal fibroblasts (DF) or lymph node cells derived from premorbid or morbid mice from the murine SLE strains (MRL-1pr/1pr, (NZB/NZW)F1), in comparison to cells derived from normal mice from the non-SLE strains (C57BL/6, BALB/c). Our results demonstrate the following. Dermal fibroblast of premorbid SLE mice showed increased susceptibility to UVA and UVB irradiation, determined by viability assay, in comparison to those of normal mice. UVB irradiation induced an enhanced expression of ICAM-1 in such SLE derived cells, in comparison to cells of normal mice. UVA and UVB increased functional activity of LFA-1 in lymph node cells of premorbid SLE mice and not in normal controls. UVB irradiation induced increased production and secretion of pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha) in DF of premorbid SLE mice, in comparison to normal controls. The enhanced pro-inflammatory responses to UVR were also observed in experiments conducted with cells derived from morbid SLE mice. In conclusion, the pro-inflammatory proneness detected in the premorbid stage of murine SLE could be of major importance in SLE pathogenesis. Furthermore, it suggests that the autoimmune inflammatory process in vivo, triggered initially by immune complex deposition, could be further amplified by UVR.

Mitochondria-based photodynamic anti-cancer therapy

As photodynamic therapy (PDT) becomes established as a treatment for cancer, there is increasing interest in identifying critical mechanisms of cell killing and understanding the bases for effective photosensitizers. The existence of multiple cellular targets makes it difficult to distinguish the critical events leading to cell death from PDT. However, with more sensitive techniques to detect photosensitizer localization, the isolation of PDT-resistant and -sensitive mutants and the use of innovative molecular and biochemical strategies to map cellular events occurring during and after photosensitization, some order is emerging from the chaos. The subcellular localization of many photosensitizers and the early responses to light activation indicate that mitochondria play a major role in photodynamic cell death. PDT with many agents which damage or inhibit different or multiple mitochondrial targets has many of the desirable characteristics for an effective anti-cancer therapy.

Transient protection by peripheral benzodiazepine receptors during the early events of ultraviolet light-induced apoptosis

The peripheral benzodiazepine receptor (PBR) is a mitochondrial protein involved in the formation of mitochondrial permeability transition (PT) pores which play a critical role during the early events of apoptosis. PBRs are located in many tissues and are strongly expressed in the superficial layers of human epidermis. PBRs play a protective role against free radical damage and PBR ligands modulate apoptosis. To investigate the role of PBR during the early events of ultraviolet (UV)-mediated apoptosis we compared the effects of UVB on PBR-transfected Jurkat cells and their wild type counterparts devoid of any PBR expression. Results indicate that early after UVB exposure (up to 4 h), PBR-transfected cells were more resistant to apoptosis and exhibited a delayed mitochondrial transmembrane potential drop, a diminished superoxide anions production, and a reduced caspase-3 activation. Taken together these findings suggest that PBR may regulate early death signals leading to UV induced apoptosis.

Low-dose ultraviolet B radiation synergizes with TNF-alpha to induce apoptosis of keratinocytes

High-dose ultraviolet B (UVB) irradiation is known to induce apoptosis of keratinocytes, but low-dose UVB dose not. In this paper we present evidence that low-dose UVB can induce TNF-alpha-dependent apoptosis of keratinocytes. In our study, 5 mJ/cm(2) doses of UVB were not sufficient by themselves to induce apoptosis of cultured human keratinocytes, but 20 mJ/cm(2) doses of UVB were. The combination of 5 mJ/cm(2) doses of UVB and exogenous TNF-alpha (15 ng/ml) induced significant apoptosis of keratinocytes, although exogenous TNF-alpha without UVB did not. This phenomenon was accompanied by enhanced clustering of tumor necrosis factor receptor 1 (TNFR1). TNF-alpha's promotion of the induction of apoptosis by low-dose UVB was seen until 30 min after irradiation but not at 1 h. We confirmed this finding using a skin organ culture system. UVB (20 mJ/cm(2)), which did not induce transformation of epidermal keratinocytes into sunburn cells, induced apoptosis when TNF-alpha was added to the culture medium. These results suggest that one of the possible mechanisms of inducing keratinocyte apoptosis by low-dose UVB and TNF-alpha is that low-dose UVB augments ligand-binding-induced TNFR1 clustering, resulting in increased apoptotic cell death.

EPR analysis of radicals generated in ultrasound-assisted lipoplasty simulated environment

The generation of various radicals by application of continuous wave (CW) high-intensity ultrasound energy (HIUE) to an aqueous biologic medium containing spin traps, under conditions simulating ultrasound-assisted lipoplasty (UAL), was demonstrated by EPR spectroscopy. The addition of water- soluble antioxidants, ascorbic acid and glutathione to the wetting solution substantially reduces the levels of hydroxyl radicals in the sonicated medium. These findings provide direct evidence for the generation of cavitation in the simulated intercellular environment, corroborating previous data, and pointing out that generation of transient cavitation in clinical UAL and other therapeutic and surgical applications of ultrasound is possible. The findings indicate that the effect of transient cavitation in aqueous biologic media may be similar to the effects of ionizing radiation, and raise the question of the long-term biosafety of the use of CW HIUE in UAL. The introduction of biocompatible water-soluble antioxidants to the sonicated medium may be utilized to suppress accumulation of radicals and reduce their possible adverse effects.

UV doses of Americans

The UV doses of Americans were never measured, but are needed for assessing the risks of UV-related health effects. We calculated these doses using a novel approach. The Environmental Protection Agency's (EPA) National Human Activity Pattern Survey (NHAPS) recorded the activity profiles of 9386 Americans over 24 months to assess their exposure to environmental pollutants, one of which is UV radiation. NHAPS used randomized telephone interviews to get their previous day's minute-by-minute activities. From NHAPS we extracted only the outdoor-daylight data of the northern and southern indoor workers (95%), stratifying by season, sex and age (0-21, 22-40, 41-59 and 60+ years) to find the average time Americans spend outdoors. Knowing the total daylight time and that while outdoors Americans are exposed to about 30% of the available solar UV (on a horizontal plane), we calculated their percent ambients. The average American's percent ambients are 2.6 and 2.5% for northern and southern females, respectively, and 3.5 and 3.6% for northern and southern males, respectively. Men over 40 years of age have the highest ambients (4%). From their ambients we calculated their annual doses using seasonal averages of UV measurements taken daily for over 2 years by EPA Brewer spectrophotometers located in four quadrants of the United States: Atlanta, GA; Boston, MA; Bozeman, MT and Riverside, CA. The average erythemal UV doses of Americans are about 25,000 J/m2/year, 22,000 for females and 28,000 for males, or 33,000 J/m2/year including a conservative continental U.S. vacation (7800 J/m2). Thus, we can now assess the risks of UV-related health effects for Americans.